Two widespread industrial chemicals can cause infertility in fish down to at least the fourth generation: The plastics chemical bisphenol A (BPA) and a key ingredient in human birth control pills, according to a study conducted by researchers from the U.S. Geological Survey (USGS) and published in the journal Scientific Reports.

“We were looking at things that can be important in reproduction and survival, the fertilization rate and the survival of embryos,” researcher Donald Tillit said.

Prior studies have shown that certain pollutants can induce changes that are passed on to offspring.

“What we know now is it can occur in fish,” Tillit said. “Now we know that fish exposed can pass the effects to offspring several generations down.”

Grandchildren, great-grandchildren affected

The study was conducted in the laboratory, where researchers exposed developing fish embryos to BPA or to 17a-ethinylestradiol (EE2, a major ingredient in oral contraceptives). Both chemicals have been confirmed as endocrine disruptors that can cause developmental disorders.

The fish were observed and allowed to reproduce, and their offspring were also observed for three generations. Other than the original generation, none of the fish were exposed to the chemicals.

No reproductive abnormalities were observed in the exposed fish, or in their offspring. The third generation of exposed fish (the “grandchildren”), however, exhibited a 30 decrease in fertility compared with fish whose ancestors had never been exposed. The next generation (“great-grandchildren”) had a 20 percent drop in fertility.

“If those trends continued, the potential for declines in overall population numbers might be expected in future generations,” researcher Ramji Bhandari said. “These adverse outcomes, if shown in natural populations, could have negative impacts on fish inhabiting contaminated aquatic environments.”

“This study shows that even though endocrine disruptors may not affect the life of the exposed fish, it may negatively affect future generations.”

The multigenerational effects observed likely belong to the field of epigenetics, which studies the way that changes in gene expression (rather than the DNA itself) can be passed on to future generations. Studies have shown that everything from BPA and pesticides to changes in the maternal diet can cause epigenetic changes down to four or more generations.

Endocrine disruptors widespread

The chemicals studied are both widespread in the environment, and like other pollutants they tend to concentrate in aquatic environments.

BPA is a chemical used to make plastics hard and transparent, and also to make resins that line food and beverage cans – both of which can cause it to leach into human food and from there into the water supply. BPA is also used in a variety of common non-food consumer and industrial products, including electronics and even the paper used to print receipts.

In recent years, concerns over the health effects of BPA have led to a proliferation of “BPA-free” products. Unfortunately, studies suggest that these substitutes have the same health effects as BPA.

EE2 is a major ingredient in birth control pills, and about 68 percent of all EE2 in such pills has been shown to pass out of the body unchanged in urine or excrement.

Even though EE2 passes into the environment in such large quantities, a 2010 USGS study showed that the amount of estrogen released into drinking water by birth control pills is utterly dwarfed by the amount released from other sources, such as livestock operations and soy and dairy foods. This just goes to show the massive scale on which human are flooding the environment with out-of-place hormones.

This flood of hormones may be one reason for the recently observed phenomenon of male fish in U.S. rivers changing into females. This is also being studied by the USGS.